Improvement in bridge-trusses



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' F. scHwATKA.

Bridge Trusses.

Witnesses: JKM

SSheetIS-SheetS. F. SCHWATKA.

I Bridge ATrussevs.

No. 141,293. Parenredjuuly 29,1873.

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ITED STATES PATENT OFFICE.

FREDERICK SG HWATKA, OF UNITED STATES ARMY, NOW AT NORTH PLATTE,

` NEBRASKA. i

IMPROVEMENT IN BRIDGE-TRUSSES.

Specification forming part of Letters Patent No. 14] ,293, dated July 29, 1873; appi-cation filed April 2G, 1873.

To all whom it may concern:

Beit known that I, FREDERICK SGHWATKA, of North Platte, in the-county ot' Lincoln and State of Nebraska, have invented a new and useful Improvement in BridgeTruss7 of which' the following is a specitication:

Figure 1, Sheet l, is a side view of a portion ot' my improved bridge/truss. Fig. 2, Sheet 2, represents the base beam. Fig. 3, Sheet 2, is a cross-section of one of the beams through the line a a, Fig. 1. Fig. 4, Sheet 2, is a cross-section of one ofthe beams through the line b b, Fig. 1. Fig. 5, Sheet 2, is a cross-section of one ofthe beams through the line o c, Fig. 1-. Fig. 6, Sheet 2, is a detail section through the line d d, Fig. 1. Fig. 7, Sheet 2, is a detail cross-section of the base beam through the line e c, Fig. 1. Fig. 8, Sheet 2, is a detail section at a point where three beams meet the top beam. Fig. 9, Sheet 2, is a detail section at a point where two beams meet the top beam. Fig. 10,

Sheet 3, is a det-ail view, illustrating the plan of construction of the truss.

Similar letters ot' reference indicate corresponding parts.

The invention consists in the improvement of truss-bridges, as hereinafter described and pointed out in the claims. A

In the following description the truss is assumed to be one hundred and twenty feet long. Upon the base beam is laid o'rl a num ber of equal divisions, A B, B C, C D, D E. The base beam is subjected to no strain oi' extension, and acts only to hold the points A B C D E together. The point U is the center ot' the base beam, and the points A B C are connected with the corresponding end a of the top beam by the beams A a B a O a. A similar construction is used at the other end of the truss, and the points C I) E are connected with the other end u of the top beam.

by the beams G a D n E n. Upon the two beams C a C n, taken as two forces, are constructed, at the point C, the resultant C z of said forces, which intersects the top beam at its central point i. The point i is connected with the points D E upon one side and the points BA upon the other. Taking the lines D i and D a, their resultant-D lis constructed,

and the resultant E l of the lines E i and E n, and also the resultant C l ofthe lines C t and C n. forces, we construct resultants, as C k for iOl,Dkforz'Dl,D m-forl D-n,Em forl E m. D l will be both a resultant for k D m, and also a resultant fort' D a. In this serial construction of the parallclogram ot' forces we lnd three points, a a af, .at which the resultants, reaching entirely across the width ofthe span, cross or intersect by threes. These points are taken as new and secondary centers of forces, from which new radial resultants are constructed, which may be called secondary resultants, in contradistinction to those that extend entirely across the width of the span. By this construction the distance upon the top beam between any two consecutive points ot' intersection ot' the resultants will be seven and a half feet. Should it be desired to subdivide these spaces it can be done by the construction ot' new primary resultants, forming new secondary centers, and new secondary resultants, reducing the spaces to three and three-fourths feet. This subdivision may be carried on indefinitely. Fig. l() represents a truss in which the distances be tween the primary centers A B C, 85e., are eqial, and also equal to the distances between the end centers A E and the piers or abutments my. The distance between the end primary centers and the piers may be only halt' the distance between the primary centers. This will allow one more primary center to be introduced into the span, increasing the strength ofthe truss proportionately, and giving two upright resultants instead of one, but no upright resultant in the center. This construction allows the braces and counterbraces to be lnade'shorter, thus increasing their streng-th and decreasing the Weight of the bridge. `In this construction the centers are upon the longer lines, which gives points of support to these long lines Whenever they are subject to compression, thus materially increasing their resisting power to deflecting strains and strains of torsion. In thisconstruction, also, theV mass of the iron is thrown toward the top beam, thus allowing a liberal use of' wrought-iron in place of castliron.

Upon these lines, as another system of The various parts ot' the bridge may be constructed as follows: The beams A a, A i, B a, B i, and C a, being subjected only to a strain of' extension, are made of wrought-iron, are elliptical in their cross-section, as shown in Fig. 5, and are arranged with their minor axes perpendicular to the truss, and their major axes in the plane of the span. Thebeams O k, G l, D Z, andE l, being subjected, also, to a strain of compression, are built up of wroughtiron beams constructed as follows: Two beams, having right-angled anges formed upon their side edges, are bolted back to back, as shown in Fig. 4, the line 1 2 being in the plane of the truss, and the distances 3 4 and 5 6 being equal.

The beams E m, D k, and C i, being subject still more to compression and less to extension than those previously described, are constructed as follows: Four wrought-iron beams, having right-angled flanges upon their side ed ges, are bolted together, as shown in Fig. 3. The parts used in forming the beams shown in Fi gs. 3 and4 are exactly alike, so that they may beusedindiscriminatelyforformingeitherkind of beam, and they all have bolt-holes formed through their bodies and iianges, in such postions that when put together they will correspond in position.

'lhe beams shown in Fig. 3 may be strengthened by keys driven into the holes in the iian ges of the outer parts, and extending along he anges of the inner parts, as shown in 1n building up the beam shown in Fig. 3 the parts should break joints. In the beam C z', in the spaces formed by the anges, should be secured cast-iron beams or cores to better enable said beam to support the extreme strain of compression to which it is subjected. The top beam a i is made similar to the beam C t', but should be much stronger, especially toward the center. The beam A C is simply a tie-rod of wrought-iron, and may be of any desired form in cross-section.

The primary beams E n,D n,(l 11E ,and D should be single beams. The primary beams E m, E l, D l, and D k are double or in twos, placed upon each side of and clamped to the single beams just mentioned.

At the points of intersections of the beams are fitted saddles or sockets, which are securely bolted to the beams that pass entirely through them, and are made with proper receptacles for the ends of the beams that do not pass entirely through them, which beams, if subjected to a strain ot' extension, should be se curely bolted in said sockets.

Having thus described my invention, I claim as new and desire to secure byvLetters Patent- 1. A truss-bridge having each beam combined with two other beams traversing the width of span, and meeting in sets of three or more, as herein shown and described.

2. The beams G k, Sac., formed ot' two beams, made with right-angled langesalong their side edges, and bolted back to back, substantially as shown and described.

3. The beams E m, &c., formed of four beams, made with right-angled ilanges along their side edges, and bolted to each other in the manner herein shown and described.

FREDK. SCHWATKA.

Witnesses:

A. T. FLINT, ANsoN MILLS. 

